Effects of alpine meadows with different degradation gradients on the stability of the soil micro-foodweb in the Tibetan Plateau

Resource-transfer connections among bacteria, fungi, and microbivorous nematodes play an integral role in the decomposition pathways of soil micro-foodweb. Exploring the response of soil bacteria, fungi, and nematodes to grassland degradation is crucial for predicting the direction and trajectory of degradation. However, the knowledge about soil bacteria-fungi-nematode interactions in ecosystem function and nutrient cycling must be highlighted properly, especially in the Qinghai-Tibet Plateau. Therefore, this study focuses on four alpine meadows at different degenerate gradients (non-degraded grassland, slightly degraded grassland, moderately degraded grassland, and severely degraded grassland) on the Qinghai-Tibet Plateau. The investigation of soil bacteria-fungi-nematode interactions uses high-throughput sequencing and correlation network analysis. The results demonstrate significant variations in the composition of soil nematode genera, and bacterial and fungal phyla, across different degradation stages. Moreover, the diversity of nematodes, bacteria and fungi declined as grassland degradation worsened. Principal component analysis (PCA) revealed that alpine meadows with varying degradation gradients significantly influenced the community structure of bacteria, fungi, and nematodes. Mantel analysis indicated that soil water content (P < 0.05), total phosphorus (P < 0.05), and total nitrogen (P < 0.05) were the primary soil properties affecting the soil bacterial community. Similarly, available soil potassium (P < 0.05), microbial biomass carbon (P < 0.05), and microbial biomass nitrogen (P < 0.05) were the main soil factors influencing the soil fungal community. In contrast, the correlation between individual soil characteristics and soil nematodes did not reach a significant level, suggesting that a blend of physical and chemical properties regulates the soil nematode community. As grassland degradation intensified, the number of links in the interaction network of bacteria, fungi, and nematodes increased. Particularly, the networks between fungi and nematodes expanded, and the key species within each network varied with the different stages of grassland degradation. Concurrently, soil micro-foodweb decomposition pathways shifted. In the ND treatment, bacteria and fungi jointly dominated the degradation channels of the soil micro-food web, while the LD and MD treatments mainly dominated the degradation channels of fungi. On the other hand, SD treatment was dominated by bacterial degradation channels. This research adds to our theoretical understanding of meadow soil micro-foodwebs and the sustainable use of alpine grasslands in the Qinghai-Tibet Plateau.